Thin bendable bone plate for bone deficit repair and method of preparation

ABSTRACT

A flexible, bendable organic decalcified or partially decalcified bone, cortical or cancellous, adapted for use in augmentation or repair of animal skeletal structures comprising a continuous plate or sheet of natural bone, as well as dermis is described. The thickness, flexibility and tensile strength of the construct is such as to allow it to be shaped and contoured without damage to it. The composition is ultimately remodeled by the body, thus obviating the need for additional surgical intervention. The clinical indications for the use of the invented construct are many, but are particularly prominent in dentistry, oral and maxillofacial surgery and implantology. It is particularly useful in the maxillary sinus augmentation. A unique new method, different from previously described methods for the preparation of the disclosed constructs, is described.

FIELD OF INVENTION

The present invention relates to the preparation of allogeneic,xenogeneic and autologous implants for use in the repair or replacementof portions of the human skeletal system, particularly those formed bymembranous ossification. In particular, it is directed toward the use insurgical procedures such as mandibular augmentation, sinus elevation,guided tissue regeneration, closure of nasal oral fistula, closure ofthe cranial defects and related procedures. The invention disclosesimplants which cause induction of bone regeneration, as well as theprocess for making the same.

BACKGROUND

Mammalia bone is made up of matrix in which are encased immature cellsas well as osteocytes. The organic portion of the matrix is composed ofcollagen, polymucosaccarides, osseous channels and related compounds andstructures. The inorganic portion of the bone which contributes to thecharacteristic harness of the bone is hydroxyapatite, a form of calciumphosphate.

If the inorganic component is partially or completely removed, theremaining organic bone matrix can be transplanted into an animal andwill reform new bone. No adverse effects are typically associated withsuch transplantation. The rate of reformation and degree of successfuloutcomes is variable, however, as each bone has its own requirements forhealing, immobilization, and bone grafting. Thus there is a need forimproved implants.

SUMMARY OF THE INVENTION

In one aspect, a flexible organic bone plate comprises a continuoussheet of partially or fully decalcified natural bone. The thickness ofthe sheet may be 1.5 millimeters or less. The sheet may contain aplurality of irregular perforations with serrated edges. In oneembodiment, channels radiate out from the plurality of irregularperforations. The plurality of irregular perforations may vary in sizeand shape. In one embodiment, the plurality of irregular perforationscomprise cross-sectional areas defining stellate, quadrangular,triangular or hexagonal shapes, or a mixture thereof. In one embodiment,the thickness of the sheet is between 0.045 millimeters and 1.5millimeters. In some embodiments, the bone plate is adapted for use inaugmentation or repair of animal skeletal structures. The natural bonemay be from a mammal. In one embodiment, the mammal is a human. Theirregular perforations with serrated edges may be configured tofacilitate ingrowth of cells and vasculature from preexisting sources ofcartilage or bone tissue at a faster rate compared to a bone sheet ofsimilar thickness having regular perforations without serrated edges. Insome embodiments, the bone plate is free-dried.

In another aspect, a process for the production of an organic bone platehaving a predetermined thickness comprises decalcifying, eitherpartially or completely, a bone which has been harvested from a bonedonor and cutting the bone after the decalcifying into one or moresheets having a thickness 1.5 mm or less. The process may furtherinclude harvesting the bone from the bone donor. The bone donor may be avertebrate, for example. In one embodiment, the vertebrate is a human.The process may further comprise processing the bone to removesubstantially all blood and lipid residue prior to the decalcifying. Inone embodiment, the decalcifying comprises contacting the bone withEDTA, citric acid, hydrochloric acid, or combinations thereof. In onesuch embodiment, the decalcifying comprises contacting the bone withcitric acid. In another such embodiment, the decalcifying comprisescontacting the bone with EDTA and citric acid. In yet another suchembodiment, the decalcifying comprises contacting the bone with EDTA,citric acid, and hydrochloric acid. The process may further comprisecreating a plurality of irregular perforations having serrated edges oneither the bone after the decalcifying or the one or more sheets of thebone after the cutting. In one embodiment, the plurality of perforationsare created by punching, burring, drilling, or lasering the sheet. Theplurality of perforations may further include channels radiatingtherefrom. In one embodiment, the plurality of perforations comprise oneor more perforations having a cross-sectional area that defines astellate, quadrangular, triangular or hexagonal shape. In oneembodiment, the cutting comprises utilizing a sharp blade to cut thebone.

In yet another aspect, a method for the in vivo repair or replacement ofa section of an animal skeletal system comprises affixing, to thesection of the animal skeletal system, a flexible organic bone platecomprising a continuous sheet of partially or fully decalcified naturalbone having a thickness of 1.5 millimeters or less, wherein thecontinuous sheet comprises a plurality of irregular perforations havingserrated edges defined therein configured to facilitate ingrowth ofcells and vasculature from preexisting sources of cartilage or bonetissue at a faster rate compared to a bone sheet of similar thicknesshaving regular perforations without serrated edges. In one embodiment,the one or more irregular perforations having a cross-sectional areadefining a stellate, quadrangular, triangular or hexagonal shape. Theplurality of irregular perforations may include channels radiatingtherefrom.

In still yet another aspect, a flexible organic bone plate comprises acontinuous sheet of partially or fully decalcified natural bone. Theflexible organic plate is obtained by the process of: (i) decalcifying,either partially or completely, a bone from a bone donor; (ii) cuttingthe decalcified bone from step (i) into one or more sheets ofdecalcified bone having a thickness of 1.5 mm or less using a sharpblade; and (iii) creating a plurality of irregular perforations havingserrated edges on the one or more decalcified bone sheets of step (ii).The irregular perforations may be created by punching, burring orlasering the one or more decalcified bone sheets. The irregularperforations may further comprise a cross-sectional area that definesastellate, quadrangular, triangular or hexagonal shape. In oneembodiment, the process further comprises harvesting the bone from thebone donor. In a further embodiment, the process further comprisescreating channels radiating out from the irregular perforations. In oneembodiment, the decalcifying comprises contacting the bone with EDTA,citric acid, hydrochloric acid, or combinations thereof In one suchembodiment, the decalcifying comprises contacting the bone with citricacid. In another such embodiment, the decalcifying comprises contactingthe bone with EDTA and citric acid. In yet another such embodiment, thedecalcifying comprises contacting the bone with EDTA and hydrochloricacid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Decalcified bendable cortical bone plate with round perforationsaccording to various embodiments.

FIG. 2. Device for producing round holes in decalcified bone plates ormembranes or for making perforations in freeze-dried dermis or othermembranous structures according to various embodiments. The shape of theperforations can be altered by changing the shape of tubes used toproduce the holes.

FIG. 3. Decalcified cancellous bone plate. Trebeculae serve asperforations. These plates are prepared from endosteum according tovarious embodiments.

FIG. 4. Irregular perforations in freeze-dried dermis according tovarious embodiments,

FIG. 5. Decalcified cortical bone being cut with a sharp blade in aSteddy-Riggs sectioning device according to various embodiments.

FIG. 6. Close-up view of decalcified cortical bone cut with a sharpblade according to various embodiments.

FIG. 7. Decalcified cortical bone plate 0.85 mm in thickness before itis perforated according to various embodiments.

FIG. 8. Microscopic section of a decalcified freeze-dried flexiblecortical bone plate four weeks post-implantation into an experimentalanimal according to various embodiments. The perforation in the centerhas been replaced with vascularized mesenchymal tissue of the host. Bonematrix contains osteoprogenitor cells of the host.

FIGS. 9 a-9 d: Decalcified bone plates showing irregular perforationsaccording to various embodiments. FIG. 9( a) illustrates quadrangularperforations. FIG. 9( b) illustrated irregular perforations withchannels (black arrows) extending therefrom. FIG. 9( c) illustratesstellate perforations. FIG. 9( d) illustrates regular round perforationsfor comparison.

FIGS. 10 a-10 d illustrate the flexible, bendable, malleable bone plateaccording to various embodiments. FIGS. 10( a) to 10(c) illustrate theflexibility of the decalcified bone plate. FIG. 10( d) illustrates thatthe bone plate will return to its original shape when straightened outafter bending.

FIG. 11 illustrates the bone plate of the prior art which is rigid andstiff thus allowing it to be bent only to a small degree.

FIG. 12 illustrates a comparison of the bone plate depicted in FIGS. 10a-10 d and the prior art bone plate depicted in FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

Described herein are bone plates (sometimes referred to as membranes)and variants thereof. Also described herein are methods and devices forproducing bone plates and variants thereof.

While the bone plates of the present disclosure may be referred to assimply bone plates, it is understood that the bone plates compriseorganic bone plates, such that a desirable portion of the organiccomponent of the bone has been retained and a significant portion of theinorganic component of the bone has been removed, e.g., completely orpartially removed. For example, according to various embodiments, theinorganic portion of the bone may be decalcified by contacting the bonewith citric acid, ethylene diamine tetraacetic acid (EDTA), and weakhydrochloric acid. In various embodiments, the contacting of the bonewith citric acid is configured such that the citric acid demineralizesthe bone slowly and gently to thereby avoid complications, such asdestruction of the bone matrix, encountered with the use of stronghydrochloric acid.

As described herein, the completely or partially decalcified bone matrixis preferably sliced into thin sheets. The thin sheets are flexiblewhile retaining tensile strength such that they may be manipulated todesired conformations. Such sheets or membranes further retain manybiologic properties related to osteogenesis. According to the presentdisclosure, such sheets may be prepared using methods that avoidlimitations that may be associated with conventional preparationtechniques that, for example, require precutting un-decalcified sheetswith an expensive diamond saw blade or conventional microtome intendedfor making sections for histological examination. Rather, the presentdisclosure described cutting bone decalcified with citric acid or byother methods with a sharp thin blade. As will become more clear below,the methods of the present disclosure may therefore prepare bone platesin which beneficial proteins associated with the bone may be retained toa greater degree due to the avoidance of contacting the bone with strongacid and creating excessive heat when sectioning the bone, e.g., priorto decalcification or with a saw or conventional microtome knife.

According to various embodiments, a bone plate comprises organic boneformed in a continuous sheet of partially or fully decalcified naturalbone. The bone plate may further include one or more artificialperforations defined therein. For example, FIG. 1 depicts decalcifiedbone comprising flexible or bendable characteristics comprising corticalbone plate having round perforations produced by the device depicted inFIG. 2. Such a device may be used for producing round holes, or asdescribed below, irregular holes in decalcified bone plates or membranesor for making perforations in freeze-dried dermis or other membranousstructures according to various embodiments. For example, according tovarious embodiments, the shape of the perforations may be altered bychanging the shape of tubes used to produce the holes or perforations.

According to various embodiments, the perforations preferably defineirregular rather than round cross-sectional areas, which may be furtherdefined by uneven edges. FIG. 3 depicts another embodiment of adecalcified cancellous bone plate prepared from endosteum according tovarious embodiments. In this embodiment, trebeculae serve asperforations. In certain embodiments, the bone plate comprises one ormore artificial perforations having uneven edges that define irregularcross-sectional areas. In further embodiments, the uneven edges compriseserrated edges from which slits (or channels) may further radiate indifferent directions to thereby form a series of canals radiating fromthe senated edges of the irregular perforations, as shown in FIG. 4 andFIG. 9 b.

According to various embodiments, a method of preparing the bone platecomprises creating perforations by punching, burring, lasering orotherwise forming the perforations on the bone using, for example, apunch, burring or perforating implement, laser, or similar devices. Forexample, in some embodiments, a device comprising a plurality ofperforating members defining one or more perforation shapes, such as around perforation shape as illustrated in FIG. 2 or an irregular shape,may be used to form perforations on the bone, preferably in bone thathas been decalcified. In certain embodiments, the slits forming thecanals radiating from the perforations on the surfaces of the constructmay be formed thereon by stationary drills, blades, saws, laser orsimilar devices.

It is noted that, according to various embodiments, the bone plateaccording to the present disclosure may be employed as allografts,autografts, or xenografts in transplantation procedures. For example,the bone plates or variants thereof, comprising irregular perforationsdefined by serrated or uneven edges having canals radiating therefrom,as herein described, may beneficially facilitate ingrowth of the cellsand vasculature from the host bed into which the construct is implanted.Such ingrowth may include ingrowth which is accelerated compared to boneplates having conventional round perforations with even edges. Accordingto various embodiments, density or number of perforations may be variedor consistent.

In various embodiments, the bone plate as described above may be furthercharacterized by flexibility. For example, the bone plate may compriseflexibility such that it may bend or flex. In some embodiments,flexibility may comprise malleability, such that the bone plate may bebendable while retaining its tensile strength into a desired form,shape, or suitable conformation. In one embodiment, flexibilitycomprises a degree of elasticity or reversible deformation as a resultof application and removal of stress, e.g., shear, tensile, orcompressive stress. For example, the bone plate may be flexibly bent orstrained into a bent or folded conformation. Upon removal of the stress,the bone plate may then retain a portion of its pre-stress form. In theabove embodiments or another embodiment, the flexibility of the boneplate may comprise the ability to be shaped or formed into sequentialfirst, second, or third conformations upon application of sequentialstresses configured to transition the bone plate into such sequentialconformations. Thus, in one embodiment, the bone plate comprises aflexible continuous sheet of partially or fully decalcified naturalbone. The thickness of the sheet, for example, may be 1.5 millimeters orless. In one embodiment, the sheet comprises a plurality of irregularperforations with serrated edges as described above.

In various embodiments, the bone plate may be freeze-dried and thuscomprise a freeze-dried organic bone plate comprising a continuous sheetof partially or fully decalcified natural bone, wherein the thickness ofthe sheet is 1.5 millimeters or less and wherein the sheet contains aplurality of irregular perforations with serrated edges having canalsradiating therefrom. As described above, the bone plate according to thepresent disclosure is also flexible.

As introduced above, in certain embodiments, the bone plate compriseschannels radiating out from the serrated edges of the irregularperforations, such as is set forth in FIG. 9 b. Such irregularperforations may vary in shape and size. For example, the irregularperforations may comprise stellate, quadrangular, triangular orhexagonal perforations, or mixtures thereof. This list, however, isnon-limiting. Such irregular perforations with serrated edges may beconfigured to facilitate ingrowth of cells and vasculature frompreexisting sources of cartilage or bone tissue at a faster rate whencompared to a bone sheet of similar thickness having regularperforations without serrated edges.

As introduced above, the bone plate may comprise a continuous sheet ofpartially or fully decalcified natural bone. In various embodiments, thethickness of the sheet is between 0.45 millimeters and 1.5 millimeters.In an embodiment, the thickness of the sheet may be between 0.045 to 1.0millimeters, 1.0 millimeters to 1.5 millimeters, 0.75-1.25 millimetersand so forth. For example, in one embodiment, the thickness of the sheetmay be between about 1.25 millimeters to about 3.0 millimeters orthicker. Such ranges are used as shorthand for describing each and everyvalue that is in that range. Any value within the range can be selectedas the terminus of the range.

In an embodiment, the natural bone is from a mammal, including a human.In an embodiment, the bone is cancellous bone. In another embodiment,the bone is cortical bone.

In any of the above embodiments, the bone plate is adapted for use inaugmentation or repair of animal skeletal structures.

The flexible organic bone plate described herein exhibits superiorflexibility over those of the prior art. For example, as shown in FIG.10C, the bone plate may be bent without fracturing. The bone plate maybe formed into bent or folded conformations as shown in FIGS. 10A and10B. The bone plate may also return to its original shape whenstraightened out, as showing in FIG. 10D.

Also provided are methods for making flexible organic bone plates whichcomprise a continuous sheet of partially or fully decalcified naturalbone. This optionally includes excising an entire bone or part of a bonefrom a bone donor. In various embodiments, the donor can be either human(allogeneic) and animal (xenogeneic). A harvested or excised bone may beprocessed immediately or preserved according to any known preservationmethod including freezing, freeze-drying, hypothermic dehydration,chemical dehydration, immersion in a chemical solutions, etc. Partial orcomplete decalcification is carried out on thin bone plates, strips orother configurations. Decalcification can be carried out by exposingbone to citric acid, ethylene diamine tetraacetic acid (EDTA) and weakhydrochloric acid, or by other methods

A method of producing a flexible organic bone plate comprisedecalcifying the bone, as described herein, and subsequently cutting thedecalcified bone with a sharp blade. This process is further illustratedin FIGS. 5-7. FIG. 5 shows flexible decalcified bone positioned betweentwo plastic plates bone plates of a Stadie-Riggs tissue slicer. A sharpblade is positioned between the two plastic plates and is slidable tosection the bone, as illustrated in FIG. 6, into thin sheets of desiredthickness, an example of which is provide in FIG. 7. Such thin sheets ofdecalcified bone made by this process support growth of human cells invivo as set forth in FIG. 8 and produce osteogenesis in experimentalanimals. In addition, the serrated perforations with radial channelsimprove and facilitate the osteogenesis process. This method avoids theneed to cut un-decalcified bone with a diamond saw blade, or aconventional microtome. By first decalcifying the bone, using, forexample, citric acid or any other method disclosed herein, thedecalcified bone can be cut with a sharp blade rather than a saw orconventional microtome knife. Thus it avoids the use of an expensiveprecision saw and diamond blade. Sectioning of bone with a bone sawcreates heat which deactivates some proteins, despite the use ofirrigation during the process. The method of the present invention, bydecalcifying first and then cutting with a sharp blade, does not createheat and avoids the deactivation of proteins.

Thus, in one embodiment, the invention can comprise a process for theproduction of an organic bone plate having a predetermined thicknesscomprising: (i) decalcifying, either partially or completely, a bonewhich has been harvested from a bone donor; and (ii) cutting thedecalcified bone from step (i) into sheets having a thickness of 1.5 mmor less.

Also provided is a flexible perforated organic bone plate comprising acontinuous sheet of partially or fully decalcified natural bone, whereinthe flexible perforated organic plate matrix is obtained by the processof described herein. For example, in an embodiment the processcomprises: (i) decalcifying, either partially or completely, an entireor part of a bone from a bone donor; (ii) cutting the decalcified bonefrom step (i) into sheets having a thickness of 1.5 mm or less using asharp blade; and (iii) creating a plurality of irregular perforationswith serrated edges on the decalcified bone sheet of step (ii).

The present invention provides for decalcifying the bone with citricacid, ethylene diamine tetraacetic acid (EDTA) and weak hydrochloricacid. Citric acid decalcifies bone slowly and gently and avoids thecomplications, such as complete destruction of the bone matrix,encountered with strong hydrochloric acid. Citric acid does not producedeleterious effects on humans. Bone decalcified with citric acid, EDTA,or combinations thereof, with or without and hydrochloric acid can becut with a sharp blade. For example, the decalcified bone can be placedbetween two rigid plates, e.g., rigid plastic or metal plates, and cutwith a sharp blade. Alternatively, bone can be rigidly held in a vice orother device and cut by guided blades, for example. The thickness of thepreparations, for example, as shown in FIG. 1, so obtained variesbetween 0.45 mm to 1.5 mm.

Thus, in an embodiment, the decalcification of the bone in step (i)comprises decalcifying the bone with EDTA, citric acid, hydrochloricacid, or combinations thereof or by other decalcifying methods. In anembodiment, the bone is decalcified with citric acid. In anotherembodiment, the bone is decalcified with EDTA and citric acid. In afurther embodiment, the bone is decalcified with citric acid, EDTA andweak hydrochloric acid. In various embodiments, decalcifying bone asherein disclosed avoids over-decalcification of the bone therebyimproving flexibility of the bone preparation compared to bonepreparations prepared by conventional methods.

In a further embodiment, the method comprises cutting the decalcifiedbone with a sharp blade. As used herein, sharp blade includes, but isnot limited to thin flexible blades such as those manufactured byLipshaw, scalpels, thin knife blades, wires, or laser devices. Accordingto various embodiments, a sharp blade does not include a bone saw orconventional microtome.

In one embodiment, preparing the bone plate further comprises creating aplurality of irregular perforations having serrated edges on or throughthe bone sheet after either decalcifying the bone or cutting thedecalcified bone. In certain embodiments, the irregular perforations arecreated by punching, burring, drilling, or lasering the sheet. In someembodiments, the plurality of irregular perforations include channelsradiating therefrom. In one embodiment, the plurality of irregularperforations comprise perforations having cross-sectional areas definingstellate, quadrangular, triangular, or hexagonal shapes, or combinationsthereof. It is to be appreciated, however, that the cross-sectional areaof the irregular perforations may define additional geometric shapes aswell as non-geometric shapes.

In one embodiment, the process further comprises harvesting a bone froma donor, which may include a defined unit of bone or part of a definedunit of bone excised from the bone donor. In various embodiments,harvesting a bone may comprise excising bone from a donor bone, whichmay include a defined unit of bone or a part of a defined unit of boneharvested from a bone donor. In certain embodiments, the bone donor is avertebrate. In one embodiment, for example, the vertebrate is a human.Methods for harvesting a bone, or part of a bone, from a bone donor areknown in the art, e.g., as described in Malinin, T. & Temple, H. T.(2013). Musculoskeletal Tissue Transplantation and Tissue Banking. NewDelhi, India: Jaypee Brothers Medical Pub., the contents of which arehere incorporated by reference in its entirety. Common donor sites fromwhich donor bone may be harvested include, but are not limited to, theilium, tibia, fibula, and ribs. In addition, the bone may be harvestedfrom the mandible of the vertebrate. In an embodiment, the bone iscancellous bone. In another embodiment, the bone is cortical bone.

In some embodiments, the process further comprises processing theharvested bone to remove substantially all blood and lipid residue priorto the decalcification of the harvested bone. Such processing methodsare known in the art, e.g., as described in Malinin, T. & Temple, H. T.(2013). Musculoskeletal Tissue Transplantation and Tissue Banking. NewDelhi, India: Jaypee Brothers Medical Pub.

In a further embodiment, the process comprises freeze drying theresulting organic bone plate. Methods for preparing freeze driedsections of decalcified bone are known in the art, such as thosedescribed in Malinin, T. I. (1992). Acquisition and banking of boneallografts. In Habal M B, Reddi A H (Eds.), Bone grafts and bonesubstitutes (pp. 206-233). Philadelphia, Pa.: W.B. Saunders Co., whichis hereby incorporated by reference in its entirety.

According to various embodiments, the bone plate of the presentdisclosure may be employed in surgical procedures such as mandibularaugmentation, sinus elevation, guided tissue regeneration, closure ofnasal oral fistula, closure of cranial defects, among others. The boneplate prepared and comprising the characteristic features as hereindescribed may comprise a construct suitable for use as an implantconfigured to beneficially promote induction of bone regenerationsuperior to certain conventional constructs prepared by more expensiveor complex methods.

In various embodiments, a method for the in vivo repair or replacementof a section of an animal skeletal system is disclosed. The method maycomprise affixing to the section a flexible perforated organic boneplate comprising a continuous sheet of partially or fully decalcifiednatural bone, as described herein. In one embodiment, the bone platecontains a plurality of irregular perforations with serrated edges, suchas, for example, stellate, quadrangular, triangular or hexagonalperforations. In a further embodiment, the plurality of irregularperforations contains channels radiating therefrom and the surface canbe scored in a gull wing or similar pattern.

In view of the above description and examples below, one of ordinaryskill in the art will be able to practice the invention as claimedwithout undue experimentation. The foregoing will be better understoodwith reference to the following examples that detail certain embodimentsof the invention. All references made to these examples are for thepurposes of illustration and not limitation. The following examplesshould not be considered exhaustive or exclusive, but merelyillustrative.

EXAMPLES Example 1 Excision and Preparation of a Donor Bone

The bone was excised under aseptic conditions from cadaver bone. Thebone was washed and the periosteum was removed. The bone marrow wasremoved with metal brushes and the medullary cavity was washed out withcopious irrigation. Microbiological studies were conducted to assuresterility and laboratory tests were performed on the donor.

Example 2 Preparation of Freeze-Dried, Decalcified, Flexible Bone PlatesFrom Donor Bone

The bone prepared in Example 1 was wrapped and quick frozen by placementit into vapor phase of liquid nitrogen. After all microbiologicalstudies to assure sterility were completed, and laboratory reports onthe donor received, the bone was placed on a pre-cooled shelf (−40° C.)of a freeze-dryer and the vacuum pump turned on. The chamber of thefreeze-dryer was maintained at 100 millitorr of vacuum, and thecondenser at −70° C. The freeze-drying cycle was 14 days. During thelast two days of the cycle the shelf temperature was brought up to 25°C. The bone was removed from the freeze-dryer following thefreeze-drying cycle and was sectioned into 3 individual plates. Thesebone plates were placed into 10% v/w solution of citric acid for 48hours and then transferred to solutions of 5% v/w of EDTA and finallyinto 10.5N HCl for 48 hours in each. Following removal of the boneplates from the HCl solution, the bone plates where cut in aStadie-Riggs tissue slicer, as shown in FIGS. 5 & 6. Perforations indecalcified bone were made with specially prepared punches.

Example 3 Implantation of Freeze-Dried, Decalcified, Flexible BonePlates into an Experimental Animal

Freeze-dried, decalcified, flexible bone plates with round perforationsprepared at described in Examples 1 and 2 where implantedintramuscularly into athymic rats. The animals were sacrificed at 2, 4,and 6 weeks post-implantation and implants removed with surrounding softtissues. The implants and surrounding soft tissue were x-rayed,photographed and fixed in 10% formalin in Earle's balanced saltsolution. Paraffin embedded tissues were section on rotary microtomes at5-6 microns, and stained with hematoxylin and eosin and “special stains”as needed.

1-36. (canceled)
 37. A flexible organic bone plate comprising a sheet ofpartially or fully decalcified natural bone, wherein the thickness ofthe sheet is 3.0 millimeters or less, and wherein the sheet contains aplurality of irregular perforations with serrated edges.
 38. Theflexible organic bone plate of claim 37, further comprising channelsradiating out from the plurality of irregular perforations.
 39. Theflexible organic bone plate of claim 37, wherein the plurality ofirregular perforations vary in size and shape.
 40. The flexible organicbone plate of claim 37, wherein the plurality of irregular perforationscomprise cross-sectional areas defining stellate, quadrangular,triangular or hexagonal shapes, or a mixture thereof.
 41. The flexibleorganic bone of claim 37, wherein the thickness of the sheet is between0.045 millimeters and 3.0 millimeters.
 42. The flexible organic boneplate of claim 37, wherein the bone plate is adapted for use inaugmentation or repair of animal skeletal structures.
 43. The flexibleorganic bone plate of claim 37, wherein the natural bone is from amammal.
 44. The flexible organic bone plate of claim 43, wherein themammal is a human.
 45. The flexible organic bone plate of claim 37,wherein the irregular perforations with serrated edges are configured tofacilitate ingrowth of cells and vasculature from preexisting sources ofcartilage or bone tissue at a faster rate compared to a bone sheet ofsimilar thickness having regular perforations without serrated edges.46. The flexible organic bone plate of claim 37, wherein the bone plateis freeze-dried or hypothermically dehydrated.
 47. A process for theproduction of an organic bone plate having a predetermined thicknesscomprising: (i) decalcifying, either partially or completely, a bonewhich has been harvested from a bone donor; and (ii) cutting the boneafter the decalcifying into one or more sheets having a thickness of 3.0mm or less.
 48. The process of claim 47, further comprising harvestingthe bone from the bone donor.
 49. The process of claim 48, wherein thebone donor is a vertebrate.
 50. The process of claim 49, wherein thevertebrate is a human.
 51. The process of claim 47, further comprisingprocessing the bone to remove substantially all blood and lipid residueprior to the decalcifying.
 52. The process of claim 47, wherein thedecalcifying comprises contacting the bone with EDTA, citric acid,hydrochloric acid, or combinations thereof.
 53. The process of claim 52,wherein the decalcifying comprises contacting the bone with citric acid.54. The process of claim 52, wherein the decalcifying comprisescontacting the bone with EDTA and citric acid.
 55. The process of claim52, wherein the decalcifying comprises contacting the bone with EDTA,citric acid, and hydrochloric acid.
 56. The process of claim 47, furthercomprising creating a plurality of perforations on either the bone afterthe decalcifying or the one or more sheets of the bone after thecutting.
 57. The process of claim 56, wherein the plurality ofperforations are created by punching, burring, drilling, or lasering thesheet.
 58. The process of claim 56, wherein the plurality ofperforations comprise one or more irregular perforations with serratededges.
 59. The process of claim 58, where the one or more irregularperforations include channels radiating therefrom.
 60. The process ofclaim 56, wherein the plurality of perforations comprise one or moreround perforations.
 61. A method for the in vivo repair or replacementof a section of an animal skeletal system comprising: affixing, to thesection of the animal skeletal system, a flexible organic bone platecomprising a sheet of partially or fully decalcified natural bone havinga thickness of 3.0 millimeters or less, wherein the sheet comprises aplurality of irregular perforations having serrated edges definedtherein.
 62. The method of claim 61, wherein the plurality of irregularperforations having serrated edges are configured to facilitate ingrowthof cells and vasculature from preexisting sources of cartilage or bonetissue at a faster rate compared to a bone sheet of similar thicknesshaving regular perforations without serrated edges.
 63. The method ofclaim 61, wherein the plurality of irregular perforations includechannels radiating therefrom.
 64. A flexible organic bone platecomprising a sheet of partially or fully decalcified natural bone,wherein the flexible organic plate is obtained by the process of: (i)decalcifying, either partially or completely, a bone from a bone donor;(ii) cutting the decalcified bone from step (i) into one or more sheetsof decalcified bone having a thickness of 3.0 mm or less using a sharpblade; and (iii) creating a plurality of perforations on the one or moredecalcified bone sheets of step (ii).
 65. The flexible organic boneplate of claim 64, wherein the plurality of perforations comprise one ormore round perforations.
 66. The flexible organic bone plate of claim64, wherein the plurality of perforations comprise one or more irregularperforations.
 67. The flexible organic bone plate of claim 64, whereinthe plurality of perforations comprise one or more irregularperforations with serrated edges.
 68. The flexible organic bone plate ofclaim 67, wherein the irregular perforations comprise a cross-sectionalarea that defines a stellate, quadrangular, triangular or hexagonalshape.
 69. The flexible organic bone plate of claim 67, wherein theprocess further comprises creating channels radiating out from theirregular perforations.
 70. The flexible organic bone plate of claim 64,wherein the perforations are created by punching, burring or laseringthe one or more decalcified bone sheets.
 71. The flexible organic boneplate of claim 64, wherein the process further comprises harvesting thebone from the bone donor.
 72. The flexible organic bone plate of claim64, wherein the decalcifying comprises contacting the bone with EDTA,citric acid, hydrochloric acid, or combinations thereof.